1. Field of the Invention
The present invention relates to an operating device having an output shaft for rotating an object to be operated, and a valve system having such an operating device and a valve serving as the object to be operated. In particular, the present invention relates to a spring return type operating device having a return spring for rotating an object to be operated in a return direction, and a spring return type valve system having this kind of operating device and a valve.
2. Description of the Related Art
For flow control of fluid that flows through a fluid channel, such as water, steam, gas, air, and oil, valve systems of spring return type and the like are used. As exemplarily illustrated in FIG. 11, a conventional spring return type valve system includes a valve 70 inserted in a fluid channel (not shown), a return spring unit 80 mounted on the valve 70, and an electric actuator 90 mounted on the return spring unit 80.
The return spring unit 80 has a housing 81, a rotating shaft 82, and a return spring 87 interposed therebetween. The return spring unit 80 is configured so that the spring force from the return spring 87 rotates the rotating shaft 82 and a valve shaft 72 of the valve 70 coupled thereto in one direction, e.g., in the direction that closes the valve. The electric actuator 90 rotates its output shaft 92 with a motor 96 via a reduction mechanism 97 consisting of a gear train so that the valve shaft 72 coupled to the actuator output shaft 92 is rotated against the spring force of the return spring 87 through the medium of the rotating shaft 82 of the return spring unit 80.
Thus, in the spring return type valve system, the valve shaft 72 and a valve element 75 integral therewith are rotated by the electric actuator 90 to a predetermined rotational position so as to adjust the opening of the valve 70, whereby the flow rate of the fluid flowing through the fluid channel is controlled. When the energization to the actuator 90 is interrupted, the valve shaft 72 is rotated in the closing direction by the spring force of the return spring 87 to close the valve 70.
In the conventional spring return type valve system described above, the housing 81 of the return spring unit 80 includes an outer housing and an inner housing. The outer housing has a lower flange 84 thereof fixed to a flange 74 of the housing 71 of the valve 70 with bolts 100. The inner housing is fitted to a socket part 73 of the housing 71 and supports the rotating shaft 82 of the return spring unit 80. A recess 83 formed in the inner housing accommodates a joint 110 for coupling the rotating shaft 82 to the valve shaft 72. Meanwhile, the housing 91 of the electric actuator 90 includes an upper housing and a lower housing. The upper housing accommodates the reduction mechanism 97. The lower housing fits a socket part 85 of an upper flange 86 of the return spring unit 80, and has a flange 95 which is fixed to the upper flange 86 with bolts 101. The lower housing has a recess 93 which accommodates a joint 111 for coupling the actuator output shaft 92 to the rotating shaft 82 of the return spring unit 80.
As described above, in the conventional spring return type valve system, the top end portion of the valve shaft 72, the joint 110, and the bottom end portion of the rotating shaft 82 are accommodated in the recess 83 of the housing 81. The top end portion of the rotating shaft 82, the joint 111, and the bottom end portion of the output shaft 92 are accommodated in the recess 93 of the housing 91. These shafts and joints are therefore invisible from exterior, sometimes working against the assembling and disassembling operations of the valve system.
Take, for example, the case of coupling the valve shaft 72 to the joint 110. When the valve shaft 72 is fitted into the joint 110, a flat-faced part 72a formed on the valve shaft 72 must be aligned to a flat part of a fit hole formed in the joint 110. The same holds true when one end portion of the rotating shaft 82 is fitted into the joint 110, and when the other end portion of the rotating shaft 82 and the output shaft 92 are fitted into the joint 111. In FIG. 11, the reference numerals 82a, 82b, and 92a show the flat-faced parts. In the conventional system, the accommodation of the joints 110 and 111 in the recesses 83 and 93 of the housings 81 and 91 makes the directions of the flat-faced parts invisible from exterior, deteriorating the workability in coupling the corresponding ones of the valve shaft 72, the rotating shaft 82, and the output shaft 92 with the joints 110 and 111.
When such coupling operations are performed under a work environment where neither the socket part 73 between the housings 71 and 82 nor the socket part 85 between the housings 81 and 92 can be visually observed from exterior, the peripheral portions of these socket parts and the openings of the housings can possibly be damaged or deformed. In addition, foreign matter adhering to the socket parts and rust forming on the socket parts are easy to be passed undetected, so that an assembly failure can occur due to the foreign matter and rust.
In cases where the electric actuator 90 suffers a breakdown that the output shaft 92 becomes unrotatable due to such reasons as a gear breakage in the reduction mechanism 97, the electric actuator 90 is detached from the valve system for repair. On this occasion, if under a work environment where the rotational position of the valve shaft 72 cannot be observed visually from exterior, the operator can possibly remove the bolt 101 despite incomplete closure of the valve 70. In this case, the entire electric actuator 90 might rotate abruptly due to the spring force from the return spring 87. With valves of larger sizes in particular, the return spring 87 has a great spring force and it is sometimes impossible for the operator to quickly hold the electric actuator 90 from rotating with strong force. Moreover, when the electric actuator 90 is detached with the valve 70 open, the load on the return spring 87 decreases rapidly. The result is that the spring force from the return spring 87 rotates the valve shaft 72 sharply in the closing direction. Such sharp closure of the valve 70 can cause a water hammer, possibly breaking the valve 70.
In assembling/disassembling the valve system of the type shown in FIG. 11, the electric actuator 90 is detached before the lower flange 84 of the return spring unit 80 is attached to or detached from the flange 71 of the valve 70 by using a screwdriver or other tools. If the valve system is configured such that the upper flange 86 of the return spring unit 80 has a diameter considerably greater than that of the lower flange 84, or that the two flanges have a considerably small gap therebetween, the tools to loosen and tighten the bolt 100 interferes with the upper flange 86, finding the operation difficult. Using an L-tipped tool to operate laterally from the housing 81 deteriorates workability.
Moreover, in the conventional valve system shown in FIG. 11, the housing 81 of the return spring unit 80 and the housing 71 of the valve 70 are in direct contact with each other. When the object to be controlled by the valve system is hot fluid such as steam, the valve 70 becomes high in temperature. Therefore, the housing 81 also becomes high in temperature because of the heat conducting from the valve 70, which makes it difficult to detach the return spring unit 80. In addition, the heat conducting from the valve 70 thermally degrades the return spring unit 80 and the actuator 90. On the other hand, when the valve 70 is cold due to coolant fluid, the return spring unit 80 and the actuator 90 decrease in temperature with internal condensation, becoming prone to rust and short-circuit breakage.
It is an object of the present invention to provide an operating device which is capable of quick, safe attachment to and detachment from an object to be operated and can reduce the effect of heat conducting from the object to be operated.
Another object of the present invention is to provide a valve system comprising an operating device of this type and a valve serving as the object to be operated, the valve system being capable of quick, safe assembling and disassembling operations.
According to one aspect of the present invention, a spring return type operating device comprises: a yoke adapted to be mounted on an object to be operated having a rotating shaft; an actuator having a drive unit and an output shaft rotated by the drive unit, the actuator being detachably mounted on the yoke; and a spring unit detachably mounted on the yoke so as to lie between the actuator and the object to be operated. The spring unit has a rotating shaft and a return spring for producing a spring force for rotating the rotating shaft in one direction. The rotating shaft has a first end portion adapted to be coupled to the rotating shaft of the object to be operated and a second end portion coupled to the output shaft of the actuator. The yoke defines a space for accommodating at least part of the actuator and at least part of the spring unit. The space has an open face for making the coupling portions of the first and second end portions of the rotating shaft of the spring unit with the rotating shaft of the object to be operated and the output shaft of the actuator, respectively, visible from exterior.
According to the spring return type operating device of the present invention, at the occasion of mounting the spring unit and the actuator onto the yoke that is mounted on the object to be operated, it is possible to couple the first and second end portions of the rotating shaft of the spring unit to the rotating shaft of the object to be operated and the output shaft of the actuator while seeing their respective coupling portions from exterior through the open face of the space which the yoke defines. This gives the operating device excellent assembleability to the object to be operated. In addition, the effect that the heat from the object to be operated has on the spring unit and the actuator is reduced by the yoke which lies between the object to the operated and the spring unit/the actuator. More specifically, when the object to be operated is hot, the heat from the object to be operated is radiated to the ambient air through the yoke before conducting to the spring unit and the actuator. When the object to be operated is cold, the yoke exercises the function of absorbing heat from the ambient air to relieve the cooling action due to the heat from the object to be operated. In this way, the effect of the heat conducting from the object to be operated is relieved. As a result, the spring unit and the actuator improve in durability, and condensation is prevented.
In the spring return type operating device of the present invention, the drive unit of the actuator is preferably composed of an electric motor.
According to this preferred aspect, the rotational position of the output shaft of the actuator and hence the rotational position of the rotating shaft of the object to be operated can be adjusted easily and precisely by the electric motor.
The yoke preferably has a bottom wall and side walls that are extended from both ends of the bottom wall and are opposed to each other. The bottom wall of the yoke is provided with a first fitting part to which the object to be operated is attached. Second fitting parts for the spring unit to be mounted on are arranged at intermediate portions of the side walls. Third fitting parts for the actuator to be mounted on are arranged on distal end portions of the side walls.
According to this preferred aspect, the yoke is formed in a general U shape as viewed from the front. This yoke is extremely simple in configuration and capable of fabrication at low cost. The side walls of the yoke define therebetween a wide open face such as facilitates the coupling operations described above.
The second fitting parts are preferably arranged in such positions that the spring unit mounted on these second fitting parts and the first fitting part come close to each other at their opposed surfaces. The third fitting parts are preferably arranged in such positions that the actuator mounted on these third fitting parts and the spring unit mounted on the second fitting parts come close to each other at their opposed surfaces.
According to this preferred aspect, the yoke cannot be mounted on the object to be operated at its first fitting part as long as the spring unit is on the second fitting parts of the yoke. The spring unit cannot be mounted on the second fitting parts as long as the actuator is on the third fitting parts. In other words, the yoke is mounted on the object to be operated before the spring unit and the actuator are mounted on the yoke in this order. On the other hand, the actuator and the spring unit are detached from the yoke in this order before the yoke is detached from the object to be operated. In this way, the order of attachment and the order of detachment determine by themselves for safety operations. In addition, all the attaching and detaching operations can be performed from above with excellent workability. Furthermore, with the spring unit and the actuator detached from the yoke, the rotational position of the rotating shaft of the object to be operated can be visually observed from exterior for proper operations.
The first fitting part of the yoke preferably has a shaft hole and a plurality of bolt through holes. The shaft hole is formed through the bottom wall of the yoke, and the rotating shaft of the object to be operated is inserted therethrough. The bolt through holes are formed in the bottom wall concentrically about the shaft hole at regular intervals in angle. The object to be operated is provided with a plurality of bolt holes consistent with the plurality of bolt through holes.
According to this preferred aspect, the yoke is bolted to the object to be operated with the rotating shaft of the object to be operated inserted through the shaft hole in the first fitting part of the yoke. Here, the flexibility in the mounting orientation of the yoke with respect to the object to be operated determines according to the angular intervals of the bolt through holes. Therefore, the spring return type operating device can be mounted on the object to be operated in desired orientation. The bolt through holes may be circular in section. Bolt through holes of arced sections, however, allow further adjustments in the mounting location of the yoke, increasing the forming tolerances of the bolt through holes and the bolt holes.
It is preferred that the bolt through holes be long holes extending in radial directions of the shaft hole.
According to this preferred aspect, the yoke of the operating device can be mounted on various types of objects to be operated having bolt holes at different radial positions. This enhances the operating device in versatility.
The second and third fitting parts are preferably formed by cutting and erecting inward the corresponding portions of the side walls of the yoke.
According to this preferred aspect, there is no need for the second and third fitting parts to be separately formed on the yoke side walls. Thus, the fitting parts can be provided at low cost.
The second and third fitting parts are preferably arranged apart from each other as seen from above.
According to this preferred aspect, the second and the third fitting parts of the yoke can be accessed from above with improved workability.
The rotating shaft of the object to be operated or the output shaft of the actuator is preferably provided with indicating means for allowing the visual observation of a predetermined rotational position thereof (for example, a full close position or full open position), such as a pointer or a marking.
According to this preferred aspect, the rotating shaft of the object to be operated and the actuator output shaft can be easily observed visually for rotational position. This ensures safety operations.
According to another aspect of the present invention, a spring return type valve system comprises: a valve having a valve shaft arranged rotatably and a valve element integral with the valve shaft; a yoke mounted on the valve; an actuator having a drive unit and an output shaft rotated by the drive unit, the actuator being detachably mounted on the yoke; and a spring unit having a rotating shaft and a spring for producing a spring force for rotating the rotating shaft in one direction, the spring unit being detachably mounted on the yoke so as to lie between the actuator and the valve, the rotating shaft being coupled at both end portions to the output shaft and the valve shaft, respectively. The yoke defines a space for accommodating at least part of the actuator and at least part of the spring unit. The space has an open face for making the coupling portions of the end portions of the rotating shaft of the spring unit with the valve shaft and the output shaft of the actuator visible from exterior.
According to the spring return type valve system of the present invention, it is possible to couple the end portions of the rotating shaft of the spring unit to the valve shaft and the actuator output shaft easily while visually observing their respective coupling portions. In addition, the effect of heat conducting from the valve is reduced by the yoke.
Like the various aspects of the spring return type operating device described above, the spring return type valve system of the present invention may be configured in various forms for various effects.